The system water-ethanol-didodecyldimethylammonium bromide. Phase equilibria and vapor pressures

The phase diagram and the colloidal structures involved in the system water , ethanol (as a hydrotrope) and didodecyldimethylammonium bromide (as a sur factant) were determined using visual observation, optical microscopy, ligh t scattering and stopped-flow methods. The results showed as expected that addition of the ethanol to the surfactant-water lamellar liquid crystal cau sed a disordering of it to an isotropic liquid, a microemulsion. The phase equilibria at ethanol concentrations less than that to form the microemulsi on were complex with several two- and three-phase regions involving the mic roemulsion and the two lamellar liquid crystals. (C) 1999 Elsevier Science B.V. All rights reserved.